1. Field of the Invention
The present invention is directed to an exposure device that detects an alignment mark on a workpiece by a microscope, aligns a mask and workpiece and exposes a mask pattern on a workpiece. More specifically, an exposure device is provided which is adapted to move a mask without moving a workpiece and to search for a workpiece alignment mark if a workpiece alignment mark cannot be detected.
2. Description of Related Art
An exposure device is used in which a mask and workpiece are aligned to form various types of electronic devices on a workpiece, followed by exposing a pattern formed on a mask (mask pattern) onto a workpiece which is the processed material.
Aforementioned workpiece and mask are aligned by detection of a workpiece alignment mark (hereinafter abbreviated workpiece mark) formed on a workpiece and a mask alignment mark (hereinafter abbreviated mask mark) formed on a mask via an alignment microscope, followed by matching the spatial relationships of the two (for example, overlap). The workpiece mark and the mask mark are usually created at two locations and are aligned by moving the workpiece in the horizontal direction relative to the mask.
Available types of aforementioned exposure devices include an exposure device that exposes a mask pattern on a workpiece that had been divided into individual sheets (termed a sheet type exposure device) and an exposure device (termed a band-shaped workpiece exposure device) that sequentially exposes a mask pattern on a workpiece while moving a band-shaped film workpiece (band-shaped workpiece).
A conventional sheet type exposure device and a band-shaped workpiece exposure device are explained below.
(1) Sheet Type Exposure Device
FIG. 6 shows the outline structure of a sheet type exposure device.
As shown in that diagram, workpiece stage WS is laid on frame 1 so that it can move in the XYxcex8 directions (X would be the direction to the left/right in the diagram, Y would be the direction perpendicular to the plane of the paper, xcex8 would be rotation about an axis perpendicular to the XY plane) via workpiece stage movement mechanism 10. Mask stage MS that holds mask M is mounted on frame 1. Furthermore, alignment microscope 2 is mounted on frame 1 via an insertion, removal mechanism (not illustrated) during detection of an alignment mark.
Mask mark MAM and workpiece mark WAM are mounted at two locations on mask M and on workpiece W, respectively, and aforementioned mask mark MAM image and workpiece mark WAM image are received, after which mask M and workpiece W are aligned.
Photo-irradiation device 3 is mounted over alignment microscope 2 and mask stage MS, and light having exposure light is irradiated from photo-irradiation device 3 during exposure resulting in exposure of the mask pattern that had been formed on the mask on to the workpiece W.
Exposure processing using an exposure device with aforementioned structure is carried out as follows.
Mask mark MAM and workpiece mark WAM are detected by alignment microscope 2 when workpiece W is laid on workpiece stage WS. Workpiece stage WS is moved in the XYxcex8 direction by workpiece stage movement mechanism 10 so that the spatial relationships of the two coincide.
Light having exposure light is irradiated from photo-irradiation device 3 when alignment of mask M and workpiece W is completed. A mask pattern is projected, focused on workpiece W and exposure is completed.
If the conveyance precision of workpiece W is poor when detecting aforementioned workpiece mark WAM, the workpiece mark would not enter the field of alignment microscope 2 when workpiece W is laid on workpiece stage WS. In such a case, workpiece W (via workpiece stage WS) would be moved and the workpiece mark would be sought.
A method of moving a workpiece and of searching for a workpiece mark has been presented in the gazette of Japanese Kokai Publication Hei-10-22201, for example, in which nine regions of an alignment microscope are sequentially searched as a function of the field thereof in spiral fashion by moving a workpiece stage.
FIG. 7 shows an example of aforementioned spiral search procedure. Field AS of an alignment microscope is a 1.5 mm square, for example. The workpiece stage is moved in sequential spirals [1] to [8] centering on the alignment microscope in FIG. 7 in a search until the workpiece mark is detected.
In this case, the workpiece stage is moved so that the regions SS of search would overlap to permit the workpiece mark to be detected even when it is at the boundary of field AS of the alignment microscope. The width of overlapping regions SS would be suitably set in conjunction with field AS of the alignment microscope. In aforementioned case, the width would be set at 800 to 500 xcexcum, for example. If the workpiece mark is not detected in searches [1] to [8] in FIG. 7, an error would be concluded to have occurred in the operation of workpiece mark mounting itself and processing would be halted as an abnormality of an undetectable workpiece mark.
(2) Band-shaped Workpiece Exposure Device
A band-shaped workpiece would be a long film of organic material or a continuous, long workpiece of thin metal, for example. A band-shaped workpiece would be exposed by unwinding the workpiece from its roll, exposing it, and then rewinding it into a roll.
Thick workpieces (workpiece thickness t=150 xcexcm or more, for example, workpieces exceeding 250 xcexcm thickness are often used) or workpieces comprising resin film lined with copper foil (so-called stiff) workpieces have come into use recently as band-shaped workpieces.
There are cases in which the mask is moved without moving the workpiece to align a mask and workpiece when using such workpieces.
Otherwise, the righting moment of the workpiece acts in the opposing direction when attempting to move a workpiece if it is thick. Since great force must be applied by the workpiece stage to counter this righting moment, the workpiece stage movement mechanism must be enlarged and the overall device must be enlarged. Furthermore, the force holding the workpiece to the workpiece stage (for example, the force retaining a workpiece by vacuum adsorption) must also withstand the righting moment. Accordingly, the workpiece could shift from the workpiece stage and alignment would then be impossible. The mask should be moved to align the mask and the workpiece in the case of this band-shaped workpiece.
FIG. 8 shows a diagrammatic structural example of a band-shaped workpiece exposure device that moves a mask to complete alignment.
Workpiece stage WS is attached onto frame 1 as shown in the diagram, and drive roller DR to convey band-shaped workpiece Wb as well as squeeze roller SR, brake roller BR and guide rollers GR1, GR2 are mounted on frame 1.
Unexposed band-shaped workpiece Wb is wound about rewind roller R1 and it is drawn out from rewind roller R1 during exposure. The workpiece Wb is conveyed onto workpiece stage WS and each prescribed region (hereinafter abbreviated exposure region) on the band-shaped workpiece is exposed. The exposed band-shaped workpiece Wb is then rewound on take-up roller R2.
Alignment microscope 2 is mounted on frame 1 via an insertion, removal mechanism (not illustrated) during detection of each alignment mark. In addition, mask M is attached to mask stage MS. A workpiece stage movement mechanism is not mounted on workpiece stage WS to move workpiece stage WS since mask M is moved instead without moving band-shaped workpiece Wb in alignment in the case of this example. Instead, mask stage MS is attached to frame 1 via mask stage movement mechanism 4 and mask stage MS is moved in XYxcex8 directions.
Two mask marks MAM are formed on mask M and two workpiece marks WAM are formed in each exposure region of band-shaped workpiece Wb. Aforementioned mask mark MAM image and workpiece mark WAM image are received by alignment microscope 2, and mask M is moved and aligned with band-shaped workpiece Wb.
Photo-irradiation device 3 is mounted over mask stage MS and alignment microscope 2. Light having exposure light is irradiated from photo-irradiation device 3 during exposure and a mask pattern is exposed on each exposure region of the band-shaped workpiece Wb.
Exposure processing is carried out as follows in an exposure device with aforementioned structure.
A prescribed amount of band-shaped workpiece Wb that is unwound from rewind roller R1 is conveyed by rotation of drive roller DR to the right in the diagram. An exposure region of band-shaped workpiece Wb reaches a prescribed position on workpiece stage WS.
Band-shaped workpiece Wb is fixed in place by vacuum adsorption on workpiece stage WS. Alignment microscope 2 is then inserted.
A mask mark MAM image and a workpiece mark image are received by the alignment microscope 2, are then fed to an image processor which is (not illustrated), and the alignment of mask mark MAM with workpiece mark WAM is detected. The spatial data are fed to a control unit (not illustrated). The control unit moves mask stage MS in the XYxcex8 directions so that mask mark MAM and workpiece mark WAM will overlap to complete alignment of mask M with band-shaped workpiece Wb.
When alignment is completed, alignment microscope 2 is withdrawn, light including exposure light is irradiated from photo-irradiation device 3, and exposure is carried out so that a mask pattern formed on mask M would be projected, focused on the band-shaped workpiece Wb.
When exposure processing is completed, irradiation of light having exposure light from photo-irradiation device 3 is terminated, vacuum adsorption on workpiece stage WS is released, drive roller DR is actuated and band-shaped workpiece Wb is moved until the next exposure region of band-shaped workpiece Wb reaches a prescribed position on workpiece stage WS.
Band-shaped workpiece Wb is conveyed by the rotation of drive roller DR, for example, as mentioned above. However, there are cases in which the position of band-shaped workpiece Wb deviates slightly relative to workpiece stage WS because of problems associated with the conveyance precision, the termination precision, and slight undulation during conveyance. There are also cases in which the position of workpiece mark WAM relative to workpiece W is inherently off due to problems associated with the precision of the equipment that mounted workpiece mark WAM in the preceding step.
Even if alignment microscope 2 is inserted at a set position after conveyance of band-shaped workpiece Wb has halted, workpiece mark WAM may still deviate from field AS of alignment microscope 2 in such cases. Specifically, the detection of workpiece mark WAM may be impossible.
Spiral searching in the search for workpiece mark WAM as explained in FIG. 7 would be possible if band-shaped workpiece Wb could be moved in such a case.
In the previous device of FIG. 6, the relative positions of mask mark MAM and alignment microscope 2 would not change since alignment microscope 2 and mask M are not moved if the workpiece is moved and workpiece mark WAM is sought. Accordingly, alignment would be possible if workpiece mark WAM were detected.
However, aforementioned spiral-shaped search by moving the workpiece W would not be possible in the device of FIG. 8 since band-shaped workpiece Wb could not be moved even if workpiece mark WAM should deviate from the detection range of alignment microscope 2 when aligning mask M with band-shaped workpiece Wb by moving mask M while fixing alignment microscope 2. Accordingly, the mask M could not be aligned with the workpiece W in this case.
The present invention was devised in light of aforementioned circumstances. The purpose is to provide an exposure device that moves and aligns a mask with a workpiece in which a workpiece alignment mark could be sought even if the workpiece alignment mark should deviate from the field of an alignment microscope. After its detection, the mask could be aligned with the workpiece.
In accordance with embodiment of the present invention, aforementioned problems of prior art devices are resolved in the following manner.
(1) A mask alignment mark formed on a mask and a workpiece alignment mark formed on a workpiece are detected by an alignment microscope and the mask is aligned with the workpiece in an exposure device that copies a pattern formed on a mask onto a workpiece. A mask stage move means that moves a mask stage MS holding aforementioned mask, an alignment microscope that is integrated with aforementioned mask stage MS, and a control means that moves aforementioned mask to align it with a workpiece, are mounted in such a device.
When aforementioned control means detects an alignment mark using aforementioned alignment microscope, aforementioned mask stage and alignment microscope are moved together to search for the workpiece alignment mark if the workpiece alignment mark is not within the field of the alignment microscope. Once the mask alignment mark and the workpiece alignment mark enter the field of the alignment microscope, the mask stage MS can be moved and the mask can be aligned with the workpiece.
(2) A mask alignment mark formed on a mask and a workpiece alignment mark formed on a workpiece are detected by an alignment microscope and the mask is aligned with the workpiece in an exposure device that copies a pattern formed on a mask onto a workpiece. A mask stage move means that moves a mask stage holding aforementioned mask, a means for moving aforementioned alignment microscope, and a control means that moves aforementioned mask to align it with a workpiece, are mounted in such a device.
If the workpiece alignment mark is not within the field of the alignment microscope when detecting the alignment mark using aforementioned alignment microscope, aforementioned control means moves the aforementioned alignment microscope in a search for the workpiece alignment mark. After the workpiece alignment mark has been detected, the mask is moved over the same distance as the distance which the alignment microscope was moved and the mask stage would then be moved to complete alignment of the mask and workpiece once the mask alignment mark and the workpiece alignment mark had entered the field of the alignment microscope.
The alignment microscope and mask are moved in a search for a workpiece alignment mark, as indicated above, if the workpiece alignment mark should not fall within the field of an alignment microscope. Consequently, a workpiece alignment mark can be detected and alignment can be completed even in a device with a workpiece such as aforementioned band-shaped workpiece which cannot be moved.
Furthermore, a workpiece alignment mark can be sought using a simple structure if the mask stage holding a mask and an alignment microscope are integrated so that the position relative to the alignment microscope does not change.